Quorum sensing. Quorum sensing is a system of stimulus and response correlated to population density.
Many species of bacteria use quorum sensing to coordinate gene expression according to the density of their local population. In similar fashion, some social insects use quorum sensing to determine where to nest. In addition to its function in biological systems, quorum sensing has several useful applications for computing and robotics. Plant cell. Plant cell structure A large central vacuole, a water-filled volume enclosed by a membrane known as the tonoplast that maintains the cell's turgor, controls movement of molecules between the cytosol and sap, stores useful material and digests waste proteins and organelles.A cell wall composed of cellulose and hemicellulose, pectin and in many cases lignin, is secreted by the protoplast on the outside of the cell membrane.
This contrasts with the cell walls of fungi (which are made of chitin), and of bacteria, which are made of peptidoglycan.Specialized cell-to-cell communication pathways known as plasmodesmata, pores in the primary cell wall through which the plasmalemma and endoplasmic reticulum of adjacent cells are continuous.Plastids, the most notable being the chloroplast, which contains chlorophyll, a green-colored pigment that absorbs sunlight, and allows the plant to make its own food in the process known as photosynthesis. Root. Primary and secondary roots in a cotton plant Large, mature tree roots above the soil Anatomy Root growth Roots of trees Early root growth is one of the functions of the apical meristem located near the tip of the root.
Over time, given the right conditions, roots can crack foundations, snap water lines, and lift sidewalks. Growth from apical meristems is known as primary growth, which encompasses all elongation. The vascular cambium produces new layers of secondary xylem annually. Rhizome. Stored rhizomes are subject to bacterial and fungal infections making them unsuitable for replanting and greatly diminishing stocks.
However rhizomes can also be produced artificially from tissue cultures. The ability to easily grow rhizomes from tissue cultures leads to better stocks for replanting and greater yields. The plant hormones ethylene and jasmonic acid have been found to help induce and regulate the growth of rhizomes, specifically in Rheum rabarbarum (rhubarb). Ethylene that was applied externally was found to affect internal ethylene levels, allowing for easy manipulations of ethylene concentrations. Knowledge of how to use these hormones to induce rhizome growth could help farmers and biologists producing plants grown from rhizomes more easily cultivate and grow better plants. See also References Jump up ^ ῥίζωμα. Rhizosphere. An illustration of the rhizosphere. A=Amoeba consuming bacteria; BL=Energy limited bacteria; BU=Non-energy limited bacteria; RC=Root derived carbon; SR=Sloughed root hair cells; F=Fungal hyphae; N=Nematode worm The rhizosphere is the narrow region of soil that is directly influenced by root secretions and associated soil microorganisms. Soil which is not part of the rhizosphere is known as bulk soil.
The rhizosphere contains many bacteria that feed on sloughed-off plant cells, termed rhizodeposition, and the proteins and sugars released by roots. Bacteria. Bacteria ( Most bacteria have not been characterised, and only about half of the bacterial phyla have species that can be grown in the laboratory. The study of bacteria is known as bacteriology, a branch of microbiology.
Etymology Origin and early evolution Morphology Many bacterial species exist simply as single cells, others associate in characteristic patterns: Neisseria form diploids (pairs), Streptococcus form chains, and Staphylococcus group together in "bunch of grapes" clusters. Even more complex morphological changes are sometimes possible. Cellular structure. Soil. Parasitism. Unlike predators, parasites typically do not kill their host, are generally much smaller than their host, and will often live in or on their host for an extended period.
Both are special cases of consumer-resource interactions. Parasites show a high degree of specialization, and reproduce at a faster rate than their hosts. Classic examples of parasitism include interactions between vertebrate hosts and tapeworms, flukes, the Plasmodium species, and fleas. Parasitism differs from the parasitoid relationship in that parasitoids generally kill their hosts. Herbivore. A deer and two fawns feeding on foliage A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage, for the main component of its diet.
As a result of their plant diet, herbivorous animals typically have mouthparts adapted to rasping or grinding. Horses and other herbivores have wide flat teeth that are adapted to grinding grass, tree bark, and other tough plant material. Pathogenicity. Pathogenicity is the potential capacity of certain species of microbes or viruses to cause a disease.
Pathogenicity is characterized by complex pathogenic properties which evolve during their struggle for existence. Pathogens are characterized by specific actions. Each species is able to give rise to different infectious processes. It is often used interchangeably with the term "virulence", although virulence is used more specifically to describe the relative degree of damage done by a pathogen, or the degree of pathogenicity caused by an organism. A pathogen is described partly through its virulence by its ability to produce toxins, enter tissue, colonize, hijack nutrients, and its ability to immunosuppress the host. Fungus. A group of all the fungi present in a particular area or geographic region is known as mycobiota (plural noun, no singular), e.g.
"the mycobiota of Ireland". Etymology The English word fungus is directly adopted from the Latin fungus (mushroom), used in the writings of Horace and Pliny. This in turn is derived from the Greek word sphongos/σφογγος ("sponge"), which refers to the macroscopic structures and morphology of mushrooms and molds; the root is also used in other languages, such as the German Schwamm ("sponge") and Schimmel ("mold"). The use of the word mycology, which is derived from the Greek mykes/μύκης (mushroom) and logos/λόγος (discourse), to denote the scientific study of fungi is thought to have originated in 1836 with English naturalist Miles Joseph Berkeley's publication The English Flora of Sir James Edward Smith, Vol. 5. Characteristics.
Filamentation. Filamentation is the anomalous growth of certain bacteria, such as E. coli, in which cells continue to elongate but do not divide (no septa formation). Bacterial filamentation is often observed as a result of bacteria responding to various stresses, including DNA damage or inhibition of replication. This may happen, for example, while responding to extensive DNA damage through the SOS response system. Nutritional changes may also cause bacterial filamentation. Unicellular organism. Some organisms are partially uni- and multicellular, like Dictyostelium discoideum. The other can be unicellular and multinucleate, like Myxogastria and Plasmodium.
‘Candidatus Magnetoglobus multicellularis’, related to Deltaproteobacteria, is a multicellular prokaryote. It is neither unicellular, nor a colony. Valonia ventricosa. Valonia ventricosa, also known as "bubble algae" and "sailors' eyeballs", is a species of algae found in oceans throughout the world in tropical and subtropical regions. It is one of the largest single-cell organisms. Characteristics Valonia ventricosa typically grow individually, but in rare cases they can grow in groups.
Sporocarp (fungi) In fungi, the sporocarp (also known as fruiting body or fruit body) is a multicellular structure on which spore-producing structures, such as basidia or asci, are borne. The fruiting body is part of the sexual phase of a fungal life cycle, with the rest of the life cycle being characterized by vegetative mycelial growth and asexual spore production. Mycelium. Fungal mycelium Microscopic view of a mycelium. This image covers a one-millimeter square. Another microscopic view of a mycelium. Numbered ticks are 230 µm apart. Mycelium as seen under a log Is this the largest organism in the world? Through the mycelium a fungus absorbs nutrients from its environment.